Body density scan result-matched orthopedic implants and methods of use

ABSTRACT

A method of treating a patient who requires surgical implantation of an orthopedic implant is described. The method includes the steps of: determining the DEXA scan T-score of the patient&#39;s native bone at a site of surgical implantation where the implant will be in contact with the patient&#39;s native bone; retrieve from among three or more implants of the same type an implant that has a density that is closest to the density of the patient&#39;s native bone at the site of surgical implantation based on the DEXA scan T-score of the patient&#39;s native bone; and implanting the retrieved implant in the patient to the exclusion of the other two or more implants.

RELATED APPLICATIONS

This application claims priority from U.S. Provisional PatentApplication Ser. No. 62/433,345 filed Dec. 13, 2016, which isincorporated herein by reference in its entirety.

BACKGROUND

This invention relates generally to the field of orthopedic surgeryinvolving orthopedic implants to correct or repair damaged bones,cartilage, vertebral discs and other musculoskeletal structures. Suchsurgery may include implants such as interbody fusion cage implants forspinal surgery to replace damaged or diseased vertebral discs,interspinous fixation implants, full or partial knee replacementimplants, full or partial hip replacement implants and the like.

In patients scheduled to undergo orthopedic surgery, bone quality in thearea of surgical intervention and implantation affects the safety andlongevity of the prosthetic implant. For example, in patients undergoingjoint arthroplasty of the hip, the bone quality around the joint affectsthe safety and failure rate and useful life span of the implant. BMD canalso affect strategies employed in spinal fusion in osteoporotic spines.

Bone mineral density (“BMD”) is a clinical marker for bone strength.Bone mineral density varies among different body regions and also variesas a result of age, disease, injury, general health, weight,demographic, and use of certain medications or hormones.

Although BMD at the site of intervention is correlated with long-termresults, bone density scans of the diseased or damaged site are notalways performed and even when they are performed, they do not affectthe course of treatment in terms of the specific implant that is used.Thus, there is a one size fits all standard of care when it comes toorthopedic implants as they relate to the bone density of the areasurrounding the implant.

Bone density scans are typically done using a dual energy x-rayabsorptiometry (“DEXA”) scan. A DEXA scan is a means of measuring bonedensity by directing two x-ray beams with different energy levels at thepatient's bone at the diseased or injured site or the site of diagnosisfor age-related routine scans to determine BMD. When soft tissueabsorption is subtracted out, the BMD can be determined from theabsorption of each beam by the bone. DEXA scans are the most widely usedand most thoroughly studied bone density measurement technology fordetermining the density of bone.

Bone density scans prior to an orthopedic implant are not always thestandard of care. For example, in one study, orthopedic surgeons wereasked if BMD is important to them in performing hip arthroplasty (MaierG S, Kolbow K, Djorde L, Maus U. The Importance of Bone Mineral Densityin Hip Arthroplasty: Results of a Survey Asking Orthopaedic Surgeonsabout Their Opinions and Attitudes Concerning Osteoporosis and HipArthroplasty. Adv. In Orthopedics. 2016, Article ID 8079354). 72% of allasked orthopaedics reported to use cementless implants as a standard inhip arthroplasty, and over 60% reported that low BMD is a reason toreconsider operation strategies, such as using cement if the patient haslow BMD. However, only 4% performed BMD measurement preoperatively.

Another example where BMD is an important factor, albeit one that is nottypically considered, in patient treatment is spinal fusion implants,including those that employ PEEk or titanium cages. Especially in olderpatients with osteoporosis, low BMD at the site of fusion is associatedwith poor fusion rate and bone stability. Various interventions havebeen proposed to address this problem, but most interventions focussimply on poor screw fixation or screw loosening and fixation failure.Many techniques have been employed to enhance the pullout strength ofthe pedicle screws that fix cages to the vertebrae. The preparation forscrew hole or minimization of tapping hole can affect the pulloutstrength in osteoporotic bone and, although the anatomical constraintsvary with patients, bigger and longer screws have been used to improvefixation to fragile bones. Other solutions involve the angulation of thescrews and screw positioning in areas of higher BMD, either of which mayincrease pullout strength. These techniques may enhance fixation, butthey still don't address the core problem of implant failure thatresults from poor bone BMD around the implant.

In fact, the current standard of care considers BMD around the site ofintervention mainly as a factor to determine whether or not to perform aprocedure, and sometimes, as discussed above, BMD is used as a factor toalter fixation methods, such as the screws. Otherwise, BMD is mostlyused as a means of diagnosing the progression of osteoporosis in olderpatients, and is not a factor in the use and type of orthopedicimplants.

Clinically, stiffening of the functional spinal unit (FSU) is aconsequence of surgical intervention for fusion. While such a conditionis unavoidable, Applicants believe that more focus is needed ondeveloping a mechanical configuration that will provide sufficientstability yet not result in stress shielding due to an overly stiffconstruct. For example, as it relates to titanium cage interbody spinalfusion implants, the modulus of elasticity for trabecular bone has beenreported to be approximately 0.10 GPa, while titanium displays a modulusof 110 GPa, and reinforced PEEK has a modulus of approximately 18 GPa.In short, the implants and the surrounding bone don't match, and therehas been no focus in the clinic or the scientific literature on thismismatch and whether it leads to a higher than necessary incidence offailure in implants over time.

For example, in the case of spinal fusion, Applicants believe thatinterbody cage stiffness can affect surgical outcomes, particularly inosteoporotic bone. Unwanted subsidence or collapse of the vertebralendplates is an unfortunate result that happens too frequently. Thepatient's bone density scan is able to reveal the level of osteoporosisin the subject patient but no bone scan density result-matched interbodycage with semi-customized interbody implant is available at the presenttime, nor has such a matched method of intervention been contemplateduntil the present invention. Certainly there has been no effort to matcha patient's DEXA scan with an implant that closely approximates the DEXAscan so that the implant and the surrounding bone at the site ofintervention are similar in density. Nor has such a method beenconsidered as a means of improving long-term outcome for patients withorthopedic implants, such as interbody spinal fusion cage implants orhip implants, among others.

There is a need to improve results in orthopedic implants. There is aneed to customize implants based on the health and strength of the boneat the site of intervention. There is a need to improve fusion andminimize failure at the site of fusion. There is a need to deliverimplants that match the mechanics of the surrounding tissue so that thenew and the old are adapted to one another and one is not prone to causethe failure of the other. These are needs that have not been addresseduntil now.

SUMMARY

One object of the invention is to provide a spine surgery fusion productthat has variable stiffness designs in order to match patients' bonedensity and be as close as possible to the modulus of the patient's ownbone modulus. The modulus of elasticity variation of one embodiment ofthe current invention can be achieved by making the design hollow tocreate a “soft-cage” that has lower, medium or higher material density,and the various optional densities can be used to best match the implantto the bone at the site of intervention.

In various embodiments, the implants described herein can bemanufactured from implantable metal, plastic, reinforced plastic,titanium, titanium cobalt, stainless steel, cobalt-chromium alloys,titanium and cobalt mixed metal, ceramic, PEEK or carbon fiber. Theinterbody cages described herein can be manufactured employing wellknown traditional manufacturing methods or newer methods such as 3-Dprinting.

In one embodiment, a kit for orthopedic surgical procedures is provided.The kit has three or more orthopedic implants of the same type. Thefirst implant has a first density, the second implant has a seconddensity that is lower than the first density, and the third implant hasa third density that is lower than the first and second densities. Otherthan the density of the implants, the three implants are the same inouter dimension and will otherwise fit within the same space of asurgical site of intervention. The kit also includes instructions foruse during a surgical procedure on a patient. The instructions includethe following steps: determine the DEXA scan T-score of the patient'snative bone at a site of surgical intervention;

-   -   i. if the DEXA scan T-score of the patient's native bone is −1        or higher, then retrieve the first implant and introduce it to        the patient's native bone to the exclusion of the second and        third implants;    -   ii. if the DEXA scan T-score of the patient's native bone is        between a −2.5 and −1.0, then retrieve the second implant and        introduce it to the patient's native bone to the exclusion of        the first and third implants; and    -   iii. if the DEXA scan T-score of the patient's native bone is        lower than −2.5, then retrieve the third implant and introduce        it to the patient's native bone to the exclusion of the first        and second implants.

In one embodiment, the implants are interbody cages for spine fusion. Inother embodiments, the implants are femoral stems of a hip implant oracetabular components of a hip implant.

In another embodiment, a method of treating a patient who requiressurgical implantation of an orthopedic implant is described. The methodincludes the steps of: determining the DEXA scan T-score of thepatient's native bone at a site of surgical implantation where theimplant will be in contact with the patient's native bone; retrieve fromamong three or more implants of the same type an implant that has adensity that is closest to the density of the patient's native bone atthe site of surgical implantation based on the DEXA scan T-score of thepatient's native bone; and implanting the retrieved implant in thepatient to the exclusion of the other two or more implants. In oneembodiment, the implants are interbody cages for spine fusion. In otherembodiments the implants are femoral stems of a hip implant oracetabular components of a hip implant.

Other objects and advantages of the present invention will becomeapparent from the following descriptions, taken in connection with theaccompanying drawings, wherein, by way of illustration and example,various embodiments of the present invention are disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings constitute a part of this specification and includeexemplary embodiments to the invention, which may be embodied in variousforms. It is to be understood that in some instances various aspects ofthe invention may be shown exaggerated or enlarged to facilitate anunderstanding of the invention.

FIG. 1 is a perspective view of a kit of three interbody spinal fusioncage implants.

FIG. 2 is a perspective view of one of the interbody spinal fusion cageimplants from the kit of FIG. 1 with anchors and an anchor plate.

FIG. 3 is a side view of the interbody spinal fusion cage implant ofFIG. 2.

FIG. 4 is a perspective view of an anchor used in the interbody spinalfusion cage implant of FIG. 2.

FIG. 5 is a perspective view of an anchor plate used to secure theanchors of the interbody spinal fusion cage implant of FIG. 2.

FIG. 6 is a top side view of the anchor plate of FIG. 5.

FIG. 7 is a DEXA Scan T score chart of the prior art.

DETAILED DESCRIPTION

Exemplary embodiments of the invention are shown in the accompanyingfigures and described below.

A bone mineral density (BMD) test provides a snapshot of bone health byproviding a value associated with bone density. The more dense the bone,the healthier and stronger it is. The test is typically performed toidentify osteoporosis, determine risk for fractures (broken bones), andmeasure response to osteoporosis treatment. It is not presently used todetermine the appropriate density of an orthopedic implant for a patientundergoing an orthopedic surgical procedure requiring an implant.

The most widely recognized BMD test is called a central dual-energyx-ray absorptiometry, or central DEXA scan. The DEXA scan can measurebone density at the hip, spine and other bones. A DEXA scan measures BMDand compares it to that of an established norm or reference standard togive the patient a DEXA Scan score. The DEXA scan score is called aT-score, which is a value that compares the patient to an ideal or peakbone mineral density of a healthy 30-year old adult. A score of 0 meansthe BMD is equal to the norm for a healthy young adult. Differencesbetween the patient's BMD and that of the healthy young adult norm aremeasured in units called standard deviations (SDs). The more standarddeviations below 0, indicated as negative numbers, the lower thepatient's BMD, meaning the less dense the bone. A DEXA scan T-scorebetween +1 and −1 is considered normal or healthy. A DEXA Scan T-scorebetween −1 and −2.5 indicates low BMD, although not low enough to bediagnosed with severe osteoporosis. A DEXA scan T-score of −2.5 or lowerindicates osteoporosis and means that the BMD is very low. The greaterthe negative number, the more severe the osteoporosis and the less densethe bone. Thus, when the DEXA scan T-score is between +1 and −1 (or ishigher than −1), the BMD of the bone is normal. When the DEXA scan scoreis between 1 and 2.5 SD below the young adult mean (−1 to −2.5 SD), thenthe BMD is lower than normal and indicates bone that is less dense thannormal bone for that location. When the DEXA scan score is 2.5 SD ormore below the young adult mean (−2.5 SD or lower) this indicates bonedensity that is significantly below normal for bone in that location andis an indicator of osteoporosis. These scores are typically associatedwith a DEXA scan chart, such as the one shown in FIG. 7, in which thenormal range of +1 to −1 (or greater than −1) is represented in green,the below normal range of −1 to −2.5 is represented in yellow, and thevery low range below −2.5 indicating osteoporosis is represented in red.This is a standard method of depicting the DEXA scan T-score in themedical community.

DEXA scan T-scores of the spinal column are typically matched to BMD asfollows. BMD in g/cm² of about 1.10 and higher are associated with anormal bone density and are therefore given a DEXA scan T-score of atleast −1 or higher (meaning 0, +1 and higher), i.e., in the green range.BMD in g/cm² of about 0.90 to about 1.10 are associated with low bonemass and are therefore given a DEXA scan T-score of between −1 and −2.5,i.e., in the yellow range. Finally, BMD in g/cm² below about 0.90 areassociated with very low bone mass and osteoporosis and are thereforegiven a DEXA scan T-score of below 2.5, i.e., in the red range.

The present invention provides methods of treatment and orthopedicimplant kits that allow physicians to best match the implant with theirpatient's DEXA Scan T-score such that the implant that most closelyapproximates the density of the bone at the site of implantationrelative to other implants is the one that is implanted to the exclusionof the other implants of the same type. When given the choice of threeor more implants of the same type that only differ by density, surfacearea, and porosity, the surgeon can choose the implant that most closelyapproximates the patient's native bone at the site of implantation basedon the patient's DEXA Scan T-score.

One embodiment of the invention is illustrated in FIG. 1. FIG. 1 showsthree interbody spinal fusion cage implants that are part of a kit 1.Spinal fusion cage implants are well known in the art and they come invarious sizes and shapes to fit within the lumbar, thoracic or cervicalspine. One example of an interbody spinal fusion cage is the Discovery™minimally invasive cervical interbody spinal fusion cage made by AuroraSpine. There are many other examples made by many other manufacturersfrom many different shapes, sizes and materials.

Kit 1 contains cage 10, cage 11, and cage 12. It also contains aninserter 13 for inserting cages 10, 11 or 12 into the disk space inbetween two vertebral bodies in the spinal column of a patient, as wellas instructions for use (not shown). Kit 1 may also include one or moresizers to determine the correct size of interbody cage implant to insertinto the disk space. Kit 1 may also include graft material that ispacked into the hollow space B in the center of cages 10, 11 or 12. Eachof cages 10, 11, and 12 have outer dimensions that are virtuallyidentical, meaning they are the same or about the same height, width,and depth. However, they are not the same weight, and they do not havethe same density, porosity or amount of surface area. Cage 10 is theheaviest of the three cages, has the least porosity, the least surfacearea and the most density. Cage 11 weighs less than cage 10 but morethan cage 12. Cage 11 has more porosity, more surface area, and lessdensity than cage 10 but less porosity, less surface area and moredensity than cage 12. Cage 12 weighs less than both cage 10 and cage 11.Cage 12 has more porosity, more surface area, and less density than bothcages 10 and 11. Cages 10, 11 and 12 can be manufactured fromimplantable metal, plastic, reinforced plastic, titanium, titaniumcobalt, stainless steel, cobalt-chromium alloys, titanium and cobaltmixed metal, ceramic, PEEK or carbon fiber, or combinations of any ofthe above. In one embodiment, they are manufactured from titanium. Theweight, density, surface area, and porosity of the three cages differsas a result of the number and positioning of various hollow channels Athrough the cages, which run through the solid surfaces of the cages.The cage with the most number of hollow channels running through it hasthe most porosity, is the lightest in weight, is the lowest in density,and has the most surface area. Cage 12 is has the most porosity, leastdensity, lowest weight and highest surface area among the three cages inkit 1, because it has the most number of hollow channels A runningthrough its otherwise solid body. Cage 12 therefore has the leastresistance to crush under load and is most similar to osteoporotic bonehaving a DEXA Scan T-score of −2.5 or lower (in the red range of a DEXAscan T-score) as compared to cages 11 and 10. Cage 11 has fewer hollowchannels A running through it than cage 12 but has more hollow channelsA than cage 10. Cage 11 is heavier, less poros, more dense, and has lesssurface area than cage 12, but is lighter in weight, more poros, lessdense, and has more surface area than cage 10. Therefore, cage 11 ismore dense than cage 12 but less dense than cage 10 and is most similarto low density bone at the T-Score range of −1 to −2.5 (in the yellowrange of a DEXA scan T-score) as compared to the other two cages 10 and12. Cage 10 has fewer hollow channels A than both cages 11 and 12, andis therefore the heaviest in weight, least poros, most dense, and havethe least amount of surface area of cages 10, 11 and 12 of kit 1. Cage10 has the strongest resistance to crushing under load compared to cages11 and 12. Cage 10 is therefore the cage among cages 10, 11 and 12 thatis most similar to healthy bone having a DEXA scan T-score range of −1or higher (in the green range of a DEXA scan T-score) as compared to theother two cages 11 and 12.

Turning to cage 10, it has the highest density of the three cages. Inone embodiment, it has a density of about 4.40 g/cm³, but can range fromabout 3.90 g/cm³ to about 5.00 g/cm³ in density. In another embodiment,it has a density of about 3.90 g/cm³. In another embodiment, it has adensity of about 3 g/cm³, but it can range from about 2 g/cm³ to about 4g/cm³ in density. In another embodiment, it has a density of about 1.40g/cm³, but can range from about 1.10 g/cm³ to about 1.80 g/cm³ indensity. In another embodiment,

Turning to cage 11, it has a density that is in between the densities ofcage 10 and cage 12, meaning it is less dense than cage 10 but moredense than cage 12. In one embodiment, it has a density of about 3.80g/cm³, but range from about 3.30 g/cm³ to about 4.20 g/cm³ in density.In one embodiment, it has a density of about 3.30 g/cm³. In anotherembodiment, it has a density of about 2.00 g/cm³, but can range fromabout 1.00 g/cm³ to about 3.00 g/cm³ in density. In another embodiment,it has a density of about 1 g/cm³, but can range from about 0.90 g/cm³to about 1.10 g/cm³ in density.

Turning to cage 12, it has a density that is lower than both cage 10 andcage 11 of the cages in kit 1. In one embodiment, it has a density ofabout 3.20 g/cm³, but range from about 2.50 g/cm² to about 3.60 g/cm² indensity. In one embodiment, it has a density of about 2.50 g/cm³. Inanother embodiment, it has a density of about 1.50 g/cm³, but can rangefrom about 1.00 g/cm³ to about 2.5 g/cm³. In another embodiment, it hasa density of about 0.80 g/cm³, but can range from about 0.60 g/cm³ toabout 0.90 g/cm³ in density.

In another embodiment, not shown in the figures, kit 1 may contain afourth cage that is still lower in density than cage 12, and is used tomatch DEXA scan T-scores that are lower than −3 suggesting not onlyosteoporosis but potentially a fracture. In one embodiment, the fourthcage has a density of about 2.50 g/cm³, but can range from about 2.00g/cm³ to about 3.00 g/cm³ in density. In another embodiment, it has adensity of about 1.00 g/cm³ but can range from about 0.40 g/cm³ to about1.3 g/cm³ in density. In another embodiment, it has a density of about0.60 g/cm′, but can range from about 0.40 g/cm³ and about 0.70 g/cm³ indensity.

In one embodiment, cages 10, 11 and 12 have identifying indicia thatindicate whether they are the most dense (also heaviest, least porousand least surface area), middle density (middle heavy, middle porous andmiddle surface area), or least dense (least heavy, most porous and mostsurface area) of the 3 cages. For example, the cages can be numbered 1for cage 10, 2 for cage 11 and 3 for cage 12 or the reverse etched intothe cages. In another embodiment, their relativedensity/porosity/weight/surface area may be identified by a +− and =signs etched into the cages. In another embodiment, the cages may have acolor painted on an area of the cage or the entirety of the cage. Forexample, cage 10 may be green, cage 11 may be yellow and cage 12 may bered to match the typical DEXA Scan color coded results. In anotherembodiment, each of cages 10, 11 and 12 is located within a sealedpackage of its own that itself has an identifier that indicates whetherit is the most dense/least porous/heaviest/lowest surface area, middledensity/porosity/weight/surface area or least dense/mostporous/lightest/highest surface area of the cages. For example, cage 10may be in a sealed package that is green or has green markings on it;cage 11 may be in a sealed package that is yellow or has yellow markingson it; and cage 12 may be in a sealed package that is red or has redmarkings on it. The purpose of this is so that the team of surgeons andstaff that are involved in a surgical procedure can easily identifywhich of the cages 10, 11, or 12 they should use based on the DEXA scanT-score of the patient's spinal column at the site of intervention, andthey won't make a mistake by implanting the wrong cage.

FIG. 2 shows an exemplary embodiment of a cage 12 with anchors 21 andanchor plate 40. The anchors 31 and anchor plate 40 also fit and areused with cages 10 and 11 in the same manner. Each of cages 10, 11 and12 also has a center hole B where bone graft material can be packedprior to insertion into disk space within a spinal column of a patient.Anchors 21 have the same density as the cages with which they areassociated. Anchors 21 can be made with the right amount of holes orchannels A to give the anchors the density level that matches thedensity of the cage with which they are matched and packaged. Thus,anchors 21 can have the same density as cage 10, the same density ascage 11, or the same density as cage 12. Anchors 21 that are matchedwith cage 10 in density have the least amount of holes or channelscompared to anchors 21 that are matched with cages 11 or 12. Anchors 21that are matched with cage 11 in density have fewer holes or channels Athan anchors 21 that are matched with cage 12 but more holes or channelsA than anchors 21 that are matched with cage 10. Anchors 21 that arematched with cage 12 in density have the most amount of holes orchannels compared to anchors 21 that are matched with cages 11 or 12.Anchors 21 can have the same indicia identifying their density level ascages 10, 11 and 12, therefore indicating which of cages 10, 11 or 12they match. In one embodiment, anchors 21 that are matched in densitywith cage 10 are located in a sealed package with cage 10. As describedabove, the sealed package can be green in color or have green markings.And anchors 21 that are matched in density with cage 11 are located in asealed package with cage 11. As described above, the sealed package canbe yellow in color or have yellow markings. And anchors 21 that arematched in density with cage 12 are located in a sealed package withcage 12. As described above, the sealed package can be red in color orhave red markings. This way it becomes more difficult to incorrectlymatch anchors 21 with the wrong counterpart cages 10, 11, or 12.

Anchors 21 are inserted through two upper holes 20 and two lower holes30 on cage 10, 11 and 12 so that each of cages 10, 11 and 12 has fouranchors, which can anchor the cage to a set of vertebrae in the spinalcolumn of a patient. Anchors 21 that are inserted through anchor holes20 are anchored to a first vertebra (superior), and anchors 21 that areinserted through anchor holes 30 are anchored or secured to a secondvertebra (inferior) that is inferior to the first vertebra. FIG. 3 is aside view that shows the orientation and angularity of the anchorsrelative to a cage, in this case cage 12, although the same is true withcages 10 and 11.

FIG. 4 shows an anchor of the present invention. When anchoring cages tovertebra, typically screws are used in the prior art. In the presentinvention, however, anchors 21 are used instead of screws. Anchors 21have multiple ridges 24 that drive into bone and secure anchors 21 tothe vertebral bone so that the anchors won't dislodge from the bone. Thehead of the anchor 22 can be struck to advance the distal end 23 ofanchor into bone and lodge anchor 21 into bone. In alternativeembodiments, screws instead of anchors 21 can also be used, althoughthey may not be as effective in long-term stability within the bone.

Anchor plate 40 is shown in FIG. 5. Anchor plate 40 has a bayonet lock42 that locks the anchor plate 40 to any one of cages 10, 11 or 12 whenthe bayonet lock 40 mates with an opening in the center of the faces ofcages 10, 11, and 12. This prevents any anchors 21 from falling out ordisassociating from cages 10, 11 or 12. Front face 41 of anchor plate 40can be tapped to engage and secure it to a cage 10, 11 or 12. Guideposts 43 are used to engage with guide holes in the faces of cages 10,11 or 12. Like anchors 21, anchor plate 40 can be matched to the densityof cages 10, 11 or 12.

In one embodiment, each kit 1 contains the following items: (i) a sealedgreen colored package containing cage 10, four anchors 21 that arematched in density with cage 10, and an anchor plate 40 that is matchedin density with cage 10; (ii) a sealed yellow colored package containingcage 11, four anchors 21 (optional) that are matched in density withcage 11, and an anchor plate 40 (optional) that is matched in densitywith cage 11; (iii) a sealed red colored package containing cage 12,four anchors 21 (optional) that are matched in density with cage 12, andan anchor plate 40 (optional) that is matched in density with cage 12;(iv) an inserter 13 that is used to insert one of the cages into a diskspace between two adjacent vertebrae; (v) instructions for use; and (vi)bone graft material (optional).

The instructions for use of kit 1 can include the following steps foruse of the items found within kit 1:

-   -   i. determine the DEXA scan T-score of the patient's native bone        at the site of surgical intervention in the spine (this can be        done prior to the surgical procedure and be included in the        patient's medical records or chart and confirmed by the surgical        physician just prior to or during the surgical procedure;    -   ii. choose a cage from among the three cages 10, 11 or 12 that        most closely matches the native bone's BMD based on the DEXA        scan T-score of the patient's native bone at the site of        implantation by doing the following:        -   1. If the patient's native bone has a DEXA Scan T-score of            −1 or higher, i.e., in the normal range of BMD indicated by            a T-score that is in the green range, retrieve the green            package containing cage 10.        -   2. If the patient's native bone has as DEXA Scan T-score of            between −1 and −2.5, i.e., in the low range of BMD indicated            by a T-score that is in the yellow range, retrieve the            yellow package containing cage 11.        -   3. If the patient's native bone has a DEXA Scan T-score            lower than −2.5, i.e., in the very low range of BMD            indicated by a T-score that is in the red range, retrieve            the red package containing cage 12.    -   iii. Unseal the package that most closely matches your patient's        DEXA scan T-score as indicated above, and do NOT unseal the        other two sealed packages.    -   iv. Pack the bone graft material into the central hole B of the        cage (optional) that you retrieved.    -   v. Take the cage from the unsealed package, which now has bone        graft material in it (optional) and releasably couple it to the        inserter.    -   vi. Use the inserter to guide the cage into the disk space at        the site of intervention in the surgical procedure.    -   vii. Secure the cage within the spinal column using the four        anchors that are in the same sealed package (now unsealed) as        the cage that you used with this patient (optional).    -   viii. Secure the anchor plate over the exposed face of the cage        by inserting the bayonet lock of the anchor plate into the        opening on the face of the cage until it locks in place        (optional).    -   ix. Once the procedure is completed, discard kit 1.

Other embodiments of kits are also contemplated herein. For example, akit that doesn't contain anchors and the cages are self anchoring as aresult of being serrated or having other mechanisms that don't requireanchors.

The same principals discussed above with respect to interbody spinalfusion cages can be applied to other types of orthopedic implants, suchas knee implants and hip implants. In one embodiment, a hip implant kitis described, which contains at least three femoral stems, each havingouter dimensions that are virtually identical. However, they are not thesame weight, density, porosity, or surface area. The first one is themost dense, heaviest, least porous, and has the least surface area; thesecond is middle in density, porosity, weight and surface area; and thethird is the least dense, lightest in weight, most porous, and has themost surface area. The stems can be manufactured from implantable metal,plastic, reinforced plastic, titanium, titanium cobalt, stainless steel,cobalt-chromium alloys, titanium and cobalt mixed metal, ceramic, PEEKor carbon fiber, or any combination thereof. In one embodiment, they aremanufactured from titanium.

In one embodiment, each of the hip implant stems has identifying indiciathat indicates whether it is the most dense, middle density, or leastdense of the 3 stems. For example, the stems can be numbered 1, 2 and 3or the reverse etched into the stems. In another embodiment, theirdensity may be identified by a +− and = signs etched into the stems. Inanother embodiment, the stems may have a color painted on an area of thestem or the entirety of the stem. For example, the first stem that isthe most dense may be green; the second stem in middle density may beyellow; and the third stem with the least density may be red to matchthe typical DEXA Scan color coded results. In another embodiment, eachof the stems is located within a sealed package of its own that itselfhas an identifier that indicates whether it is the most dense, middledensity or least dense of the stems. For example, the first stem of thehighest density may be in a sealed package that is green or has greenmarkings on it; the second stem in middle density may be in a sealedpackage that is yellow or has yellow markings on it; and the third stemof lowest density may be in a sealed package that is red or has redmarkings on it. The purpose of this is so that the team of surgeons andstaff that are involved in a surgical procedure can easily identifywhich of the stems they should use based on the DEXA scan T-score of thepatient's hip, and they won't make a mistake by implanting the wrongstem.

In yet another embodiment, a kit contains 3 or more acetabularcomponents each having outer dimensions that are virtually identical.However, they are not the same weight, and they do not have the samedensity, porosity, or surface area. The first one is the most dense,heaviest, least porous, and has the least surface area; the second ismiddle in density, porosity, weight and surface area; and the third isthe least dense, lightest in weight, most porous, and has the mostsurface area. The acetabular components can be manufactured fromimplantable metal, plastic, reinforced plastic, titanium, titaniumcobalt, stainless steel, cobalt-chromium alloys, titanium and cobaltmixed metal, ceramic, PEEK or carbon fiber or any combination thereof.In one embodiment, they are manufactured from titanium.

In one embodiment, each of the acetabular components has identifyingindicia that indicate whether it is the most dense, middle density, orleast dense of the components. For example, the components can benumbered 1, 2 and 3 or the reverse etched into the components. Inanother embodiment, their density may be identified by a +− and = signsetched into the components. In another embodiment, the components mayhave a color painted on an area of the component or the entirety of thecomponent. For example, the first acetabular component that is the mostdense may be green; the second acetabular component in middle densitymay be yellow; and the third acetabular component with the least densitymay be red to match the typical DEXA Scan color coded results. Inanother embodiment, each of the acetabular components is located withina sealed package of its own that itself has an identifier that indicateswhether it is the most dense, middle density or least dense of thecomponents. For example, the first component of the highest density maybe in a sealed package that is green or has green markings on it; thesecond component in middle density may be in a sealed package that isyellow or has yellow markings on it; and the third component of lowestdensity may be in a sealed package that is red or has red markings onit.

In one embodiment, kit 1 is associated with a specific demographic. Forexample, it may be associated with white females, black females, whitemales, black males, Hispanic females, Hispanic males, Asian females,Asian males, or other demographics based on gender, race, ethnic origin,height, weight, physical condition, medications the patient takes,history of illness or current illness, or other factor for which theremay be a reference database for DEXA Scan T-scores. The specific kitthat most closely matches a patient can be used, because the cages inthat kit can have densities that are matched with the DEXA Scan T-scorereference database that most closely matches that patient in terms ofgender, race, ethnic origin, country of nationality or other factor.

Each of the kits described above can contain a instructions for useduring a surgical procedure on a patient. The instructions can containthe following steps, which are described with respect to a kitcontaining 3 or more implants of the same type but differentdensity/weight/surface area/porosity:

-   -   i. determine the DEXA scan T-score of the patient's native bone        at a site of surgical intervention in the spine (this can be        done prior to the surgical procedure and be included in the        patient's medical records or chart and confirmed by the surgical        physician just prior to or during the surgical procedure in        which an orthopedic implant is introduced into the patient;    -   ii. choose the implant from among the three implants that most        closely matches the native bone's BMD based on the DEXA scan        T-score;        -   1. If the patient has a DEXA Scan T-score of −1 or higher,            i.e., in the normal range of BMD indicated by a T-score that            is in the green range, choose the implant that has a green            indicia (or other indicia indicating highest density among            the three cages) or is in green packaging;        -   2. If the patient has as DEXA Scan T-score of between −1 and            −2.5, i.e., in the low range of BMD indicated by a T-score            that is in the yellow range, choose the implant which has a            yellow indicia (or other indicia indicating medium density            among the 3 cages) or is in yellow packaging;        -   3. If the patient has a DEXA Scan T-score lower than −2.5,            i.e., in the very low range of BMD indicated by a T-score            that is in the red range, choose the implant, which has a            red indicia (or other indicia indicating least density among            the three cages) or is in the red packaging.    -   iii. Introduce the implant to the patient's native bone at the        site of surgical intervention to the exclusion of the other two        implants.    -   iv. Once the procedure is completed, discard the kit.

In another embodiment, a method of treating a patient who requiressurgical implantation of an orthopedic implant is described. The methodincludes the steps of: determining the DEXA scan T-score of thepatient's native bone at a site of surgical implantation where theimplant will be in contact with the patient's native bone; choosing fromamong three or more otherwise identical implants an implant that has adensity that is closest to the density of the patient's native bone atthe site of surgical implantation based on the DEXA scan T-score of thepatient's native bone; and using said implant in the surgical procedureto the exclusion of the other two or more implants.

In one embodiment, the method of treatment involves implanting aninterbody spinal fusion cage in the spinal column. The physician ormedical team performing the surgery may determine the patient's gender,race and/or ethnic origin or this step may be skipped. The physician maydetermine other factors unique to the patient as well, such as height,weight, physical condition, the medications the patient takes, historyof illness or current illness. The physician or medical team performingthe surgery then determines the DEXA scan T-score of the native bone ateither or both the vertebra above and the vertebra below the locationwhere the cage will be implanted. Once the DEXA scan T-score isdetermined, the physician or medical team performing the surgery willchoose an interbody spinal fusion cage from among 3 or more cages thatmost closely matches the patient's DEXA scan T-score for either or bothof the vertebrae that were scanned relative to the other two implants.The DEXA scan T-score may use a general reference such as a healthyperson have peek bone at 30 years of age, or it may use a more specificreference, such as a black male. If a more specific reference is used,then a kit that is matched to that reference will be used rather than akit that is matched to a general reference. If the DEXA scan T-score isin the green range or a score of −1 or higher indicating healthy bone inthe normal range, then the cage having an indicia of highestdensity/weight and lowest surface area/porosity is chosen from among the3 or more cages. That indicia may be a number, a sign, or a color on thecage or on the packaging of the cage. For example, the cage may be in asealed package that is green or has green markings to indicate that itis the cage with the highest density/lowest porosity/greatestweight/lowest surface area. If the DEXA scan T-score is in the yellowrange or a score of between about −1 and about −2.5 indicating bone thatis lower than normal in density, then the cage having an indicia ofmedium density/porosity/surface area/weight is chosen from among the 3or more cages. Again, that indicia may be a number, a sign or a color onthe cage or on the packaging of the cage. For example, the cage may bein a sealed package that is yellow or has yellow markings to indicatethat it is the cage with the medium amount of density/porosity/surfacearea/weight from among the three or more cages. If the DEXA scan T-scoreis in the red range or a score of −2.5 or lower indicating very low bonedensity and osteoporosis, then the cage having an indicia of lowdensity/weight and high porosity/surface area is chosen from among the 3or more cages. Again, this indicia may be a number, sign or color on thecage or on the packaging of the cage. For example, the cage may be in asealed package that is red or has red markings to indicate that it isthe cage with the lowest density/weight and highest porosity/surfacearea from among the three or more cages. Once the physician or medicalteam has chosen the interbody cage based on the DEXA scan T-score of theparticular patient, that interbody cage is implanted in the spinalcolumn at the site of intervention to the exclusion of the other twocages. This process may be repeated for any further cages that are to beimplanted in the patient at other sites along the spinal column bymatching the correct cage with the site of intervention based on theDEXA scan T-score for the additional site(s) of intervention along thespinal column.

While the is susceptible to various modifications and alternative forms,specific examples thereof have been shown by way of example in thedrawings and are herein described in detail. It should be understood,however, that the invention is not to be limited to the particular formsor methods disclosed, but to the contrary, the invention is to cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the appended claims.

We claim:
 1. A kit for orthopedic surgical procedures comprising: threeor more similar orthopedic implants, wherein a first of said implantshas a first density, the second implant has a second density that islower than the first density, and the third implant has a third densitythat is lower than the first and second densities; instructions for useduring a surgical procedure on a patient comprising the following steps:determine the DEXA scan T-score of the patient's native bone at a siteof surgical intervention; if the DEXA scan T-score of the patient'snative bone is −1 or higher, then retrieve the first implant andintroduce it to the patient's native bone to the exclusion of the secondand third implants; if the DEXA scan T-score of the patient's nativebone is between a −2.5 and −1.0, then retrieve the second implant andintroduce it to the patient's native bone to the exclusion of the firstand third implants; if the DEXA scan T-score of the patient's nativebone is lower than −2.5, then retrieve the third implant and introduceit to the patient's native bone to the exclusion of the first and secondimplants.
 2. The kit of claim 1, wherein the three or more implants eachhas a unique indicia that identifies its density relative to the othersof the three implants.
 3. The kit of claim 2, wherein the indicia of thefirst implant is that it is green in color or has a green marking on it.4. The kit of claim 2, wherein the indicia of the second implant is thatit is yellow in color or has a yellow marking on it.
 5. The kit of claim2, wherein the indicia of the third implant is that it is red in coloror has a red marking on it.
 6. The kit of claim 1, wherein the three ormore implants is each within its own sealed package within the kit andeach package is a different color.
 7. The kit of claim 6, wherein thepackage of the first implant is green or has green markings, the packageof the second implant is yellow or has yellow markings, and the packageof the third implant is red or has red markings.
 8. The kit of claim 1,wherein the implants are interbody cages for spine fusion, femoral stemsof a hip implant, or acetabular components of a hip implant.
 9. The kitof claim 8, wherein the three or more implants have the same outerdimensions as one another, but the first implant weighs more than thesecond implant and the second implant weighs more than the thirdimplant.
 10. The kit of claim 9, wherein the third implant has moresurface area than the second implant, and the second implant has moresurface area than the first implant.
 11. The kit of claim 9, wherein thethird implant has greater porosity than the second implant, and thesecond implant has greater porosity than the first implant.
 12. The kitof claim 8, wherein the implants are interbody cages for spine fusion.13. The kit of claim 12, wherein the first implant has a density ofabout 4.40 g/cm³, 3.90 g/cm³, 3.00 g/cm³ or 1.40 g/cm³.
 14. The kit ofclaim 12, wherein the second implant has a density of about 3.80 g/cm³,3.30 g/cm³, 2.00 g/cm³ or 1.00 g/cm³.
 15. The kit of claim 12, whereinthe third implant has a density of about 3.20 g/cm³, 2.50 g/cm³ 1.50g/cm³ or 0.80 g/cm³.
 16. The kit of claim 12, wherein the first implanthas a density that falls within the range of about 1.10 g/cm³ to about1.80 g/cm³, the second implant has a density that falls within the rangeof about 0.90 g/cm³ to about 1.10 g/cm³, and the third implant has adensity that falls within the range of about 0.60 g/cm³ to about 0.90g/cm³.
 17. The kit of claim 8, wherein the implants are femoral stems ofa hip implant.
 18. The kit of claim 8, wherein the implants areacetabular components of a hip implant.
 19. A method of treating apatient who requires surgical implantation of an orthopedic implant,said method comprising the steps of: determining a DEXA scan T-score ofthe patient's native bone at a site of surgical implantation where theimplant will be in contact with the patient's native bone; retrieve fromamong three or more similar implants an implant that has a density thatis closest to the density of the patient's native bone at the site ofsurgical implantation based on the DEXA scan T-score of the patient'snative bone; and implanting the retrieved implant in the patient to theexclusion of the other two or more implants.
 20. The method of claim 19,wherein the implant is an interbody cage for spine fusion.
 21. Themethod of claim 19, wherein the implant is a femoral stem of a hipimplant or an acetabular component of a hip implant.
 22. The method ofclaim 19, wherein if the DEXA scan T-score of the patient's native boneis −1.0 or higher, then a first implant is retrieved, wherein the firstimplant has the highest density among the three or more implants; if theDEXA scan T-score of the patient's native bone is between −1.0 and −2.5,then a second implant is chosen, wherein the second implant has a lowerdensity than the first implant but a higher density than a thirdimplant; and if the DEXA scan T-score of the patient's native bone islower than −2.50, then the third implant is chosen, wherein the thirdimplant has a lower density than either the first implant or the secondimplant.
 23. The method of claim 22, wherein the first implant isretrieved from a sealed package that is green; the second implant isretrieved from a sealed package that is yellow; and the third implant isretrieved from a sealed package that is red.